1. Field of the Invention
The present invention relates to an endoscope and, more particularly, to an endoscope with a device to facilitate recognition of shapes of imaged objects.
2. Description of the Prior Art
The recognition of shapes of imaged objects on a display can be facilitated in an endoscope by incorporating a device for projecting patterned light beams on imaged objects and measuring deviation of an imaged pattern from the original pattern due to parallax.
The patterned light beams are provided, for example, by means of laser beams through a diffraction grating. Such a device is shown in FIG. 1. A grating 1 is constructed by combining two sheets of glass-fibres, each sheet being comprised of an array of glass-fibres, such that each glass-fibre of one sheet intersects with glass-fibres of the other sheet at right angle. As shown in FIG. 1, when laser beams 2 from a laser 3 are shone on such a diffraction grating 1, patterned beams 4 emerge from the other side which when projected on a flat screen 5 exhibit a regular array of spots as a diffraction pattern.
Now, if such patterned beams 4 are projected on an irregular surface and spots on the surface are observed from a point separated from a point from which patterned beams 4 emerged, a deviation of an observed pattern from the original pattern appears, which is a phenomenon known as a parallax. This is shown in FIG. 2, where G is the point from which the patterned beams 4 emerge, A is the point of observation, Pa is a parallax distance separating G and A, and the patterned beams 4 are projected on the irregular surface of an object 6 to be imaged. Since deviations of patterns due to parallax depend on parallax distances and shapes of surfaces, by fixing a parallax distance the information on the shape of an object can be obtained from the observation of a deviation. This can be implemented in an endoscope by fixing a diffraction grating at a certain distance away from an imaging device.
As for a measurement of deviation, the conventional method has been manual operations by an operator who identifies centers of the spots from the observations of a displayed image and registers positions of the spots on a display by means of a digitizer. It can easily be seen that such operations are extremely cumbersome as well as time consuming.
To alleviate this situation, the measurements of the positions of the centers of the spots can be handled automatically by means of the binarization of a displayed view according to a particular threshold brightness and the thinning of the spot pattern.
However, determining an appropriate threshold brightness can be very subtle, because errors such as false identifications of empty points as spots or misidentifications of spots as empty points due to smearings or noises may easily occur, and even one such error can lead to an incorrect recognition of shapes.